Now that winter has arrived and most of our wild flowers have been reduced to a mass of decaying brown stems, one little group of small ferns which are easily overlooked in the summer months now come to the fore, they are the Spleenworts, or Aspleniums to give them their Latin name.
We have four species in Berwickshire, three are common and are to be found occasionally growing in natural rock outcrops, but are much more frequent growing in lime mortar in old walls in both towns and the countryside.
The fourth species, ‘Sea Spleenwort’ is a rare species almost exclusively found on cliffs by the sea with one isolated colony on a rock outcrop near the River Tweed at Ladykirk.
The best colonies in Berwickshire for the ‘Sea Spleenwort’ are to be found in moist cracks in deep shade in the sandstones rocks at Lamberton, some plants are only a few meters from the high tide line and must frequently get covered with salt spray when there are east windsand storms. So close to the sea and with the shelter of the cliffs those plants are unlikely to experience any frost.
There are a few scattered colonies along the east coast of northern England and eastern Scotland but on the west coast and outer islands it is quite frequent, enjoying the high humidity and milder conditions found along the Atlantic shores.
The three species found growing in walls are all plants which can endure very dry conditions and are ‘resurrection’ plants, becoming all shrivelled up and almost un- recognisable when dry but returning to their normal leafy state with a shower of rain. The three species can be found growing together and are quite easy to tell apart.
The ‘Maidenhair Spleenwort’ is distinguished by having a simple black stem (or rhachis) with pairs of little rounded leaves (pinnae) along its length, which vary between one and three inches long.
‘Wall-rue’ is smaller and has a dark green stem which is branched and the leaves form a more triangular shape.
The third species is the ‘Black Spleenwort’ which if conditions are favourable will grow into fair sized clumps with leaves as much as nine inches long but if conditions are often dry they will be much smaller, the stem is black at the base and dark green near the tip and like the ‘Wall-rue’ the leaves are on branched stems and are again in a triangular shape.
If you examine the underside you will find rusty brown sori, these are where the dust like spores are produced and will be distributed far and wide in the wind and with luck land in a suitable crevice to start a new plant.